It is common for transportable mixing units, like those employed on concrete trucks, to use a plurality of hinged chute sections, for movement between a retracted transport position and an extended discharge position, and for the transfer and discharge of concrete mix from a transport vehicle. It is well known in the art that a variety of hydraulically, pneumatically, or electrically driven assemblies are available to actuate the chute deployment and retraction process. Devices representative of the prior art are described in U.S. Pat. Nos. 4,458,800; 5,056,641;and 6,918,481 assigned to the same assignee as the present application.
The vehicles themselves may be of a front or rear discharge type. In rear discharge vehicles the mechanism for discharging and delivering concrete from a mixing drum is positioned at the rear of the vehicle. And in a front discharge type, the mechanism for discharging and delivering concrete from a mixing drum is located above the vehicle's cab enclosure at the front of the vehicle.
It is well known in the art that folding chute sections utilized for the discharge and delivery of concrete from the mixing drum are typically heavy and produce large stresses on the chute joints and actuator assemblies, particularly when loaded with concrete. The operation actuator and hinge assemblies experience significant resistive and torsional forces that result in rapid damaging wear and tear upon the parts. Additionally, designs commonly employed within the industry, while successful, are inefficient as to the delivery of functional forces from the actuator system to the point of deployment because of limitations in the hinge mechanisms. U.S. Pat. No. 3,774,741 (hereafter “the '741 patent”) exemplifies this design. The embodiment depicted in FIGS. 1-7 of the '741 patent shows a traditional single eyelet hinge design. Two chute segments are rotatably linked by a pair of hinges. The hinges comprise a pair of hinge eyelets, one eyelet on each side of each chute segment. These hinges utilize a single pivot bolt to rotatably fasten the chute segments. U.S. Pat. Nos. 4,498,568 and 4,458,800 also utilize this single eyelet hinge system. U.S. Pat. No. 3,930,567 exemplifies a slight modification to the single eyelet design where extended joint arms are employed.
One common limitation with existing single eyelet hinge configurations occurs because a strong twisting force and motion results when the actuator operates as the actuator force is delivered through the joint to deploy or retract the chute segment. When actuator force is applied, inertial, gravitational, and frictional forces resist the desired rotational movement about the pivot. Delivery of the actuator force results in twisting forces at the weakest point, the rotational axis, within the system. The force will dissipate in all possible directions until the resistive forces are maximized and the movement about the hinges is the least resistive outlet for energy dissipation. The twisting forces place unwanted stress on the hinge components resulting in undue wear and tear on the components. This wear and tear on the chute joints results in excessive maintenance costs and inconvenient down time to repair the vehicle.